Subminiature sealed thumbwheel switch with indicator and stop means



1965 c. B. HUNTRESS ETAL 3,222,465

SUBMINIATURE SEALED THUMBWHEEL SWITCH WITH I CATOR D STOP ME 'led Ma 23. 196

INVENTORS CHARLES B. HUNTRESS BY HENRY .GABRIELIAN AGENT United States Patent 3,222,465 SUBMINIATURE SEALED THUMBWHEEL SWITC WITH INDICATOR AND STOP MEANS Charles B. Huntress and Henry Gabrielian, Santa Ana,

Calih, assignors to Electronic Engineering Co. of California, Santa Ana, Calif., a corporation of California Filed Mar. 23, 1964, Ser. No. 354,017 16 Claims. (Cl. 20011) Our invention relates to a multi-position switch and particularly to such a switch of small size and novel internal configuration in which contacts are sealed within a chamber.

Electronic apparatus of the present day is characterized by small size. As the number of elements has been increased in any apparatus the size of the elements has been descreased. In this trend the substitution of the transistor for the vacuum tube has been important. In general, the miniaturization of switches has lagged and in applications where small size and light weight are of importance the situation has become critical.

We have been able to produce a sealed thumbwheel switch of relatively very small size by departing from the prior art in the manner of sealing, by providing a nOVel arrangement of contacts and by arranging an optional stop assembly between the thumbwheel and the housing.

An object of our invention is to provide a small sealed rotary switch.

Another object is to obtain the contacting action of a large switch by a novel arrangement of rotor and stationary contacts in a small switch.

Another object is to provide a thumbwheel switch in which the degree of rotation of the thumbwheel can be altered externally of the switch after its original manufacture.

Another object is to provide a small thumbwheel switch which is composed of relatively few parts and which is light in Weight.

Other objects will become apparent upon reading the following detailed specification and upon examining the accompanying drawings, in which are set forth by way of illustration and example certain embodiments of our invention.

FIG. 1 shows a side elevation of our subminiature sealed thumbwheel switch at approximately four times actual size,

FIG. 2 shows a sectional elevation of the same along center-line 2--2 of FIG. 1,

FIG. 3 shows the front of a stationary contact board arranged for coaction with the rotor assembly of FIG. 5,

FIG. 4 shows a front elevation of a rotor assembly, and

FIG. 5 shows a front eleveation of an alternate embodiment of a rotor assembly for providing multiple track performance.

In FIG. 1 numeral 1 indicates an insulating board formed from epoxy-impregnated fiberglass or like material. This board carries conductive paths, with formed thereby stationary contacts, 2, 3, etc., as shown in FIGS. 2 and 3. The conductive paths and the contacts may be formed by known printed or etched circuit techniques. As disclosed in our co-pending application for Letters Patent entitled Rotary Thumbwheel Voltage-Divider Switch, Serial No. 349,319, filed March 4, 1964, the insulating board may also carry circuit elements; such as resistors or diodes. These are soldered or otherwise connected to the conductive paths, normally at the left-hand side of the board as shown in FIG. 3.

Board 1 is mounted upon a housing 4, which has a forward portion 5 coactive with the thumbwheel, a central fastening portion 6, and a rear portion 7. Forward portion 5 has a front of panel arcuate face 8, which lies adjacent to thumbwheel 9 and tends to guide the finger of the operator in rotating the thumbwheel. The'fastening portion 6 is provided with holes 10, top and bottom, to allow the switch to be fastened to a panel or other support (not shown). Such an arrangement allows each switch of a gang to be separately removable. The rear portion 7 of the housing provides a further surface to accomplish sealing of the board to the housing.

Housing 4 has a centrally disposed journal 11, a recess 12 that is concentric with the journal, and a stop 14 that extends away from the recess in the housing. The housing is preferably molded, and of a thermoplastic, such as a poly-carbonate.

Stop 14 is shown dotted in FIG. 2, since it is typically in the forward half of FIG. 1 and thus should not be shown in FIG. 2. It has been shown dotted to illustrate its coaction with stop-pin 42; i.e., to prevent continuous rotation of thumbwheel 9 if one or more stop-pins are employed.

Rotor 15 has a disk shape and hub 16. It is also molded of a thermoplastic, such as a poly-carbonate, over shaft 17 as an insert. The thermoplastic shrinks upon coldness after molding and adheres to the metal shaft, which has a milled portion to assist in the adherence. The rotor is positioned within recess 12.

At least two contacts are provided upon the rotor in a typical embodiment. Of the stationary contacts, one contact, or group of contacts, 2 at one radial distance constitutes the common or return contact, while a second group 3, typically at a greater radial distance, constitutes the commutated or individual group of contacts for accomplishing plural changes in circuit connections through the use of the switch.

The corresponding rotor contacts are 20 and 21, to be seen in FIGS. 2 and 4. These are formed of one piece of spring beryllium copper, or the equivalent, and are fastened to the rotor disk 15 at appropriate circumferential points by eyelets or rivets 22. The free end of each rotor contact is provided with a specific contact, 23 and 24, respectively, of Paliney material, a palladiumsilver alloy, in a pellet-like form. These bear upon stationary contacts 2, 3, etc.,

Thumbwheel 9 is attached to shaft 17 with essentially a snug push fit. Shaft 17 is provided with a flat 25, causing the end view thereof to have a D shape. Hub 26 of thumbwheel 9 has a corresponding D shaped hole so that the thumbwheel can be attached to the shaft in only one position. This also causes the thumbwheel to drive the shaft and thereby rotor 15.

The thumbwheel has a drum portion 27, which may be translucent, and normally carries numerals from 0 through 9 sequentially disposed around the drum. Each numeral is aligned with a projection of the thumbwheel, as projection 9 in FIG. 1. Additionally, the thumbwheel has a disk portion 28, which joins hub 26 to drum 27 and forms the external surface of this part of the switch assembly.

A housing cover 30 fits over thumbwheel 9 and secures it in place axially. The cover has the same peripheral shape as housing 4, save for the fastening pourtion 6 of the housing. This results in the assembly having approximately twice the thickness as the housing alone.

Four projecting pins 31 are molded integrally with housing 4. These fit in correspondingly spaced and dimensioned holes in cover 30. Additionally, counterbores 32 are formed in the cover, extending downwardly to the ends of the projecting pins. This is to provide a well for containing solvent for the material of the housing and the housing cover during a step in the manufacturing process. The material is typically a thermoplastic, such as a poly-carbonate, and methylene chloride is a solvent. This solvent is water thin. A measured amount,

3 as a drop or two, is placed in each counterbore after the switch is assembled and is to be made a solid block insofar as the housing and the housing cover is concerned. The solvent passes between pins 31 and the holes in the cover surrounding the same by capillary action and also further downward to the fiat faces of the housing and cover which face each other at all four corners of these two elements. By employing a measured amount of the solvent and because a groove 33 extends between the fiat faces and rim 34, which surrounds the thumbwheel drum 27, anexcess of solvent does not creep beyond the opposing faces. This mode of processing provides a simple yet effective way of joining the housing and the housing cover. It should be noted that this processing does not enter into the sealing of the switch contacts into the chamber. The solvent acts as an adhesive.

The sealing of recess 12 is accomplished in part by employing a first resilient means, or O ring, 36, which surrounds shaft 17 within an annular groove in the shaft. This ring is positioned within journal 11 and so seals the shaft-journal combination. A synthetic rubber, such as Buna N (nitrile), is suitable for the material of the O ring.

We have found it desirable to employ a lubricant upon this ring. This aids in sealing. A grease of the petroleum type, such as a low temperature military specification grease having a non-creep characteristic and usable from 65 F. to +250 F., is suitable.

The sealing of recess 12 is completed by the use of a second resilient means, or O ring, 37. This ring fits within a circular groove in the face of housing 4. The groove has outwardly sloping sides to most effectively receive the O ring and to make a seal when insulating board 1 is forced in place by peening over the four eyelets 38. These eyelets are located at essentially the corners of a square circumscribing the O ring, thus they pass through the housing and the board externally thereof. The material of ring 37 is the same as that of ring 36, but a lubricant is not normally employed.

This mode of sealing is liquid, vapor and gas tight.

In the prior art it has been necessary to arrange suitable stops as projections upon elements in fabrication and/or to arrange stops Within a sealed switch prior to sealing.

According to this invention it is seen that we provide only one such projection 14, as an inherent part of the switch. A plurality of counterbore holes 40 is provided within thumbwheel 9 at a radius less than the surface of drum portion 27. Normally, one counterbore is provided for each switch position. In FIG. 1 this is a total of ten; although fewer counterbores may be provided.

In addition to the outer counterbore 40 there is the inner bore 41, which has a smaller diameter. Empty counterbores are shown in the lower part of FIG. 2, but within the upper counterbore of this figure a stop-pin 42 is shown. These pins may be screw machine products and may be fabricated of brass or steel. They may also be formed by a cold-headed process. The apertures (counterbores) are molded into the thumbwheel.

On each stop-pin is a small diameter projection with the same diameter as hole 41 which projects beyond the inner surface of the thumbwheel to engage stop 14. This 'is shown in the upper part of FIG. 2. While the stoppins may have a smooth cylindrical portion 42 we prefer to make this a straight knurled, or milled surface.

" Such a surface does not require as exact manufacturing tolerances as the smooth surface.

It is seen that if stop-pins 42 are not inserted in any of the counterbores the thumbwheel can be rotated continuously in either direction. If one stop-pin is inserted the switch can still be turned to any and all of the switching positions, but it cannot be continuously rotated. A stop of rotation is effected between the l and 0 thumbwheel positions by placing a stop-pin in the counterbore between the 1 and 2 positions. This is because the indicated positions appear at the center of the front are 8 while stop 14 is approximately away from that point at near the top in FIGS. 1 and 2.

By employing two stop-pins appropriately placed in the counterbores the rotation of the thumbwheel can be limited to from two to nine switch positions; i.e., any number less than ten of the switch positions may be used, with the remaining number blocked off from being contacted.

This provides one construction having universal application in the matter of extent of thumbwheel rotation. All of the thumbwheel switches may be manufactured alike and only one (universal) model need be held in stock. When a customer calls for switches having a certain limited rotational travel the appropriate counterbores can be filled with stop-pins and the item shipped at once. Since this is a simple operation, it can be performed by distributors or even by customers. The latter then can change the operating range of their switches even after they have been placed in service if this is desired.

It is to be noted that our thumbwheel switch may be embodied to have a fewer or a greater number of total switch positions although ten is the number used most because of the decimal numerical system.

The conductive paths upon the insulating board shown in FIG. 3 indicate how stationary contacts for the switch are formed in general and illustrate a novel arrangement by means of which the functioning of four tracks can be obtained from only two tracks in particular. Such functioning is a great advantage in subminiature sized switches. From a practical standpoint it is known that there is only suflicient radial space in such switches to accommodate two tracks. Our arrangement thus makes possible contact schemes that have heretofore been impossible in subminiature thumbwheel switches.

In FIG. 3 the inner track is exemplified by individual contact 2, while the outer track is exemplified by common contact 44. In the typical embodiment all of the contacts on the rotor 15 are electrically connected together, as shown in FIGS. 4 and 5. The rotor contact assembly is made of a single piece of beryllium copper. This requires a common, or return, contact so that the circuit to each switched contact can be completed to a stationary terminal. The common contact for the usual rotary switch is thus a complete ring and it occupies one whole track. With plural individual switched contacts in the second track a single pole multiple position (as a ten position) thumbwheel switch is formed.

It will be recognized that when the thumbwheel and thus the rotor contacts are in a given circumferential position only one circumferential area of the common stationary contact is in use. Further, with four electrically interconnected contacts as in FIG. 5 it will be seen that any one of the four contacts can constitute the rotor contact for the common return circuit. It is thus. possible to evolve a pattern for the stationary contacts in which the common contact wanders around rather than being a complete ring occupying the whole of one path.

In this way the common is on the outside track for certain switch positions and on the inside track for other switch positions. In FIG. 3 the basic common connection and stationary contact is element 44. It connects to the C (common) terminal at the left of insulating board 1. A small hole 45 is located at the right side of contact 44, which hole has a conductive coating all around the interior surface thereof.

Typically, the stationary contacts upon board 1, such as 2, 3, 44, etc., are provided by known printed circuit or photo-etch techniques. Briefly, board 1 is originally provided with an adherent coat of copper on each side. Each side is then photosensitized with a photoresist and is exposed according to the pattern of conductors desired. The unwanted copper is. etched away and the remaining photoresist removed. The several small holes shown in FIG; 3,

such as hole 45, are provided and the board is dipped in molten solder, tin or is otherwise provided with an electrically conductive coating on the inner surface of the holes according to known techniques. This coating electrically connects to the copper conductive paths on both sides of the board.

Then additional copper plating may be employed to establish a firm conductive connection through the holes from the conductive path on one side of the board to a conductive path on the other side of the board. Alternately, a plating of low stress nickel may be used, such as is employed at the same time to prepare the copper conductive paths for proper wearing qualities as stationary contacts. Gold is. then normally plated over the nickel to provide the top contacting surface. In order to preserve the sealed aspect of our switch each of the small connection holes is sealed after the above fabrication wit-h a small amount of epoxy cement that is flowed into the same.

By means of this processing We obtain interconnections between conductive paths on both sides of the insulating board. In FIG. 3, the common stationary contact 44 is interconnected through conductive hole 45 to conductive path 46 on the rear of the insulating board. Conductive path 46 is shown as a dotted line in FIG. 3 for convenience in illustrating such paths on both sides of a board in one figure, but in actuality such paths have the usual width and the circuitous paths that characterize printed circuits.

Connection through a conductive hole is made from rear conducting path 46 to the small stationary contact 47 on the inner track on the front of the board; thence via extensions of path 46 and through appropriate conductive holes to circumferentially larger stationary contact 48 on the inner track; thence to medium sized stationary contact 49 on the outer track; and finally to the small stationary contact 50 on the inner track. This constitutes the wandering common" and provides a common return circuit at Table I Position of Thumbwheel (O) (1) y (2) I (0" signifies a connection between a stationary and a rotor contact.)

The scheme of Table I provides for a 1 through output. It will be noted that the common (C) stationary contact is contacted by the rotor contact at every position of the thumbwheel. When one or more of the other contacts (1), (2), (4) or (8) are also contacted by the rotor contact the circuit is completed from the common contact to the other stationary contact involved.

In detail in FIG. 3 it is seen that stationary contact terminal (1) connects by three suitable conductive paths on the rear of board 1 and through three conductive holes to small stationary contacts 51, 52 and 53 on the inner track. In the same manner, terminal (2) connects to outer contacts 54 and 55 and to small inner contact 2. Terminal (4) connects to double circumferential length inner track contact 56; and terminal (8) connects to outer double circumferential length contact 3. It will be noted that the circumferential length of basic common contact 44 covers three switch positions.

It will be further noted that when the four spaced contacts 58, 59, 60 and 61 of FIG. 5 are turned over and caused to ride upon the stationary contacts of FIG. 3 the connections set forth in Table I are accomplished.

For example, at one time inner spaced contact 61 contacts inner stationary contact 56, inner spaced contact 60 contacts inner stationary common contact 47 and the two outer spaced contacts 58 and 59 both contact outer stationary common contact 44. Thus there is an electrical connection established between terminal (4) and common terminal (C) in FIG. 3; corresponding to position 4 in the table. Note that the connection to the common terminal through the contacts is made by three spaced and three stationary contacts as recited above. Thus, the contact resistance is considerably reduced for this switch position with respect to what it would he were there only one pair of contacts making the common contact.

In the next clockwise position, inner contacts 61 and 56 are still in contact, as are outer contacts 58, 59 and 44. However, spaced contact 60 now contacts inner stationary contact 51, which latter contact connects to terminal 1. This is the contacting configuration according to position 5 in the table; with mutual contact established between terminals (4), (1) and (C). In this position two spaced contacts make connection with a common contact, 44, and so the contact resistance is again less than were only a single pair of contacts making the common contact.

By tracing out each position of the rotor it will be found that in every position save position 7 there are either two or three pairs of contacts (rotor to stationary) in parallel in the common circuit. For position 7 there is only one pair, since the binary equivalent of 7 must be synthesized from the three contacts (1), (2) and (4), leaving only one of the spaced contacts on the rotor to contact the (C) stationary contact.

The contact configuration illustrated may be altered to read 0 through 9 rather than "1 through 10 by removing the stationary contacts connecting to terminals (2) and (8) in the 0 position of the thumbwheel. Then in the 0 position the external circuit is not completed at all; only the common rotor and stationary contacts make contact, but this does not complete a circuit.

In a similar manner, but with .a different stationary contact configuration and connections upon a new board 1, it is possible to switch according to the BCD with excess 3 code; according to the Biquinary code; according to the 9s complement BCD, or according to the 10s complement BCD.

For the BCD with excess 3 code the scheme is generally the same as illustrated, save that at each position of the thumbwheel contacts are made to give the value according to Table I, but with three added; i.e., (1) and (2) added.

The Biquinary code has three common stationary contacts; the common common (C), an even common (C and an odd common (C The line values are each now paired; as (0, 1), (2, 3), (4, 5), (6, 7) and (8, 9). Which line connection is completed depends upon which of the odd or even commons is also contacted. Thus, with the (2, 3) line contact contacted the value is 2 if the even common (C is also contacted, but the value is 3 if the odd common (C is contacted instead.

The 9s complement BCD code has essentially the circumferentially reversed stationary contact configuration of the 0-9 BCD code previously treated. For example, position 1 has the value of 91:8, position 2 has the value 9-2:7, etc. Similarly, the 10s complement BCD code has essentially the circumferentially reversed stationary contact configuration of the l-lO BCD code previously treated.

The configuration of the wandering common stationary contact system is approximately the same for all of the codes above considered and so the illustration thereof in FIG. 3 may be considered typical.

An advantage accrues with respect to wear of the rotor contacts with the wandering common system because of the presence of additional stationary contacts. It is known that contact wear, as of the Paliney alloy, is conditional upon the surface passed over and that it is considerably greater when passing over the glass-epoxy surface of board 1 than when passing over gold stationary contacts, as 2, 3. The reduction in contact resistance because of the use of the additional common contacts has already been mentioned.

All of the code embodiments and also the single pole multiple position embodiments can be provided with diodes. This is physically accomplished at the left side of board 1 of FIG. 3 near the output terminals (1), (2), (4), (8). Electrically, one diode is connected between each terminal and the remainder of the printed circuit conductors otherwise directly connected to that terminal. The diodes may be poled to hold the negative signal level at a given value and to prevent a reverse current from ever fiowing through the switch.

Isolated conductive paths 57 are provided around forward holes 38 on both sides of board 1 to increase the thickness there to the same elsewhere on the board where conductive paths are found. This prevents board 1 from being warped when the four eyelets 38 (FIGS. 1 and 2) are pressed over to secure the assembly mechanically.

In FIG. the four spaced contacts 58-61 are supported by a single piece of beryllium copper 62. The required double arcuate shape thereof may be obtained by stamping with a suitable die; or by a photoetch process as has been previously described in connection with the stationary contacts on board 1, except that the insulating board is not required.

Spring piece 62 has a central hole to receive eyelet or rivet 22'. This piece may have a thickness of the order of 0.004". An additional piece 63 has the same configuration as piece 62 at the eyelet and partially around the outer spring fingers. Piece 63 has a thickness of the order of 0.010" and is not formed of spring material. Both pieces are held to rotor disk 15 by eyelet 22'. Piece 63 is on top and acts as a stiffener for the outer springs of piece 62. These springs go to outer contacts 58 and 59 and this assembly gives equal stiffness to the outer and inner springs of piece 62.

Both pieces 62 and 63 have small holes which fit over small projections 64 and 65. The latter are molded integrally with rotor disk 15 and serve to position pieces 62 and 63 upon the rotor. This is desirable because of the single eyelet 22' employed as the main fastening.

Each of the spring arms carrying contacts 58-61 is bent upwards as shown in FIG. 5 by a substantially equal amount of 0.100" in a forming die so that a proper pressure will be exerted by the Paliney alloy contacts 58-61 upon stationary contacts 2, 3 etc. when the switch is assembled.

It is to be understood that a similar technique is employed for producing, forming and fastening the springs 20-21 of FIG. 4 as has been described above, save that an additional stiffener is not required. Each of the springs 20-21 are of equal length.

It is usual to employ a detent mechanism with thumbwheel switches to insure relatively automatic positioning at, and not between, contacting positions. One such arrangement employs spring 67, shown dotted in FIG. 1. The spring is formed of one piece of spring metal in common with bracket 68 of, say, 0.014" thick material. Two holes in the bracket pass eyelets 38 directly under the heads thereof on the upper surface of housing 4. The free, bottom end of the spring presses against the projections of thumbwheel 9 at the rear thereof and provides stable rotational equilibrium only when nested in the 8 hollow between adjacent projections, as is shown in FIG. 1.

In certain applications of our switch it is desired that the thumbwheel drum 27 be illuminated. This is accomplished by cementing a small, unbased lamp 70 atop the free surface of housing 4 just forward of journal 11 and by forming drum 27 of translucent material. A rim 71 is preferably molded upon the surface of the housing in order that the lamp will be uniformly positioned in each switch in manufacturing. The lamp has a T-l envelope and may have any of the following identifying numbers; Mil 24367-680, Mil 24367-683, CM 680, CM 683, etc.

An epoxy or quick drying cement is employed to fasten the lamp to the housing. Insulating sleeves 72, 73 are placed over the lead Wires of the lamp and these are threaded through holes in housing 4 directly under bracket 65. When the bracket is fastened in position this secures the sleeves and wires by a gentle pressure such that the insulation of the sleeves is not impaired.

While the shape and disposition of elements of this thumbwheel switch have been evolved to make manufacturing of a subminiature thumbwheel switch possible, it will be understood that our structure may also be manufactured in large sizes.

Still other modifications may be made in the arrangement, size, proportions and shape of the illustrative embodiments shown without departing from the scope of our invention.

Having thus fully described our invention and the manner in which it is to be practiced, we claim:

1. A sealed thumbwheel switch comprising;

(a) an insulating board having conductive paths forming stationary switch contacts,

(b) a housing attached to said board,

(0) a recess in said housing,

(d) a journal and a stop upon said housing,

(e) a rotor within said recess,

(f) a shaft attached to said rotor and journaled in said journal,

(g) plural contacts upon said rotor to bear upon said stationary contacts,

(11) a thumbwheel attached to said shaft, outside of said recess,

(i) first resilient means surrounding said shaft to seal said shaft within said journal While allowing rotation of said shaft,

(j) second resilient means disposed between said board and the periphery of said housing to seal said board to said housing,

(k) said first and second resilient means adapted to seal said rotor and said stationary contacts within said recess, and

(1) means upon said thumbwheel coactive with said stop to limit the rotation of said thumbwheel.

2. The thumbwheel switch of claim 1 in which said means upon said thumbwheel includes;

(a) plural apertures disposed circumferentially around said thumbwheel, and

(b) a least one stop-pin disposed within a said aperture to engage said stop and limit the rotation of said thumbwheel and said rotor.

3. The thumbwheel switch of claim 2 in which;

(a) said stop-pin is cylindrical, having a milled portion of large diameter at one end and a small diameter at the other end,

(b) said milled portion is a press fit into each of said plural apertures, and

(c) said small diameter end passes through a said aperture and engages said stop.

4. The thumbwheel switch of claim 1 in which;

(a) said second resilient means is an O ring, and

(b) said housing has a groove with sides tapered outwardly toward the top of said groove to receive said O ring.

5. The thumbwheel switch of claim 1 in which;

(a) said recess is circular and concentric with said journal, and

(b) said recess is closed by said insulating board.

6. The thumbwheel switch of claim 1 in which;

(a) said thumbwheel has indicia thereupon, and

(-b) said thumbwheel is uniquely attached to said shaft .by a single flat upon said shaft and a corresponding fiat within a central hole in said thumbwheel.

7. The thumbwheel switch of claim 1, which additionally includes;

(a) a housing cover having a central opening to receive said thumbwheel,

(b) an arcuate front face, and

(c) an additional opening in said front face to pass the projections of said thumbwheel and to expose indicia carried by said thumbwheel.

8. The thumbwheel switch of claim 7 which additionally includes;

(a) an electric lamp having leads,

(b) means to attach said lamp to said housing within said thumbwheel to illuminate the drum portion of said thumbwheel, and

(c) means to fasten said leads within the structure of said switch in which said leads are secured in joining said housing and said insulating board.

9. The thumbwheel switch of claim 1 which additionally includes;

(a) a plurality of projecting pins formed of the material of said housing,

(b) the same plurality of holes in said housing cover disposed to receive said pins, and

(c) an adhesive within each of said plurality of holes to bond said pins to said cover by initially dissolving the material of said pins and said housing cover.

10. A thumbwheel switch comprising;

(a) an insulating board having conductive paths forming two groups of stationary switch contacts at two different radii,

(b) a rotor attached to the thumbwheel of said switch,

() a housing sealed to said board and enclosingly supporting said rotor,

(d) four spaced contacts circumferentially grouped together upon said rotor,

(e) two of said four spaced contacts bearing upon substantially adjacent contacts of one of said groups of stationary contacts, and the other two of said four spaced contacts bearing upon substantially adjacent contacts of the other of said groups of stationary contacts,

(f) a common stationary contact containing at least one of said spaced contacts at every position of said thumbwheel,

(g) said common contact extending contiguously circumferentially around a portion of one said group of stationary contacts, and

10 (h) said common contact disposed only at selected positions of said thumbwheel around said other group of stationary contacts.

11. The thum bwheel switch of claim 10 in which;

(a) said four spaced contacts are electrically interconnected, and

( b) two of said spaced contacts are circumferentially disposed one thumbwheel rotary position away from the other two of said spaced contacts.

12. The thumbwheel switch of claim 11 which additionally includes;

(a) a stiffener member formed to fit over said four spaced contacts, and

(b) shaped to extend over the two said spaced contact-s which contact the outer of said two groups of stationary switch contacts to provide an equal effective free length for all of said four spaced contacts.

13. The thumbwheel switch of claim 12 which additionally includes;

(a) plural pins extending from the surface of said rotor,

(b) plural apertures in said four spaced contacts and in said stiffener member disposed to fit over said plural pins to position said four spaced contacts and said stiffener member, and

(c) only one fastening extending through said rotor, said four spaced contact-s and said stiffener member to fasten these elements together.

14. The thumbwheel switch of claim 10 in which;

(a) said common stationary contact is formed of first conductive paths upon one side of said insulating board,

(b) second conductive paths are disposed upon the other side of said insulating board, and

(c) conductive apertures pass through said insulating board to electrically join said first and said second conductive paths.

15. The thumbwheel switch of claim 14 in which;

(a) said common stationary contact is disposed with respect to said four spaced contacts to provide plural electrical connections between said common stationary contact and said four spaced contacts in a plurality of positions of said thumbwheel.

16. The thumbwheel switch of claim 14 which has;

(a) means to seal said conductive apertures to prevent the pas-sage of matter through said insulating board.

References Cited by the Examiner UNITED STATES PATENTS 2,090,505 8/1937 Uhle 200 -11 2,886,661 5/1959 Skelton et a1. 200-11 X 3,089,923 5/1963 Wright 200--l1 X 3,104,299 9/ 1963 Koci et a1.

3,171,905 3/1965 Rubio et a1. 20011 KATHLEEN H. CLAFFY, Primary Examiner. 

1. A SEALED THUMBWHELL SWITCH COMPRISING; (A) AN INSULATING BOARD HAVING CONDUCTIVE PATHS FORMING STATIONARY SWITCH CONTACTS, (B) A HOUSING ATTACHED TO SAID BOARD, (C) A RECESS IN SAID HOUSING, (D) A JOURNAL AND A STOP UPON SAID HOUSING, (E) A ROTOR WITHIN SAID RECESS, (F) A SHAFT ATTACHED TO SAID ROTOR AND JOURNALED IN SAID JOURNAL, (G) PLURAL CONTACTS UPON SAID ROTOR TO BEAR UPON SAID STATIONARY CONTACTS, (H) A THUMBWHEEL ATTACHED TO SAID SHAFT, OUTSIDE OF SAID RECESS, (I) FIRST RESILIENT MEANS SURROUNDING SAID SHAFT TO SEAL SAID SHAFT WITHIN SAID JOURNAL WHILE ALLOWING ROTATION OF SAID SHAFT, (J) SECOND RESILIENT MEANS DISPOSED BETWEEN SAID BOARD AND THE PERIPHERY OF SAID HOUSING TO SEAL SAID BOARD TO SAID HOUSING, (K) SAID FIRST AND SECOND RESILIENT MEANS ADAPTED TO SEAL SAID ROTOR AND SAID STATIONARY CONTACTS WITHIN SAID RECESS, AND (L) MEANS UPON SAID THUMBWHEEL COACTIVE WITH SAID STOP TO LIMIT THE ROTATION OF SAID THUMBWHEEL. 